The present invention relates to a printhead and an ink-jet printer (recording apparatus) using the printhead, and more particularly to a printhead (recording head) compatible with various printers and an ink-jet printer utilizing the removable printhead.
Printheads have conventionally been exchangeable in an ink-jet printer. The ink-jet printer where a plurality of printheads are exchangeable, comprises a determining terminal or a determining unit in the printhead to enable the apparatus to determine the type of the printhead, so that the apparatus can determine the type of the printhead which has just been installed.
Currently, great interests have been brought to the ink-jet printing method since it provides various advantages, for instance, noise generated at the time of printing is so little that it can be disregarded; high-speed printing is possible; a regular sheet of paper can be utilized; particular processing such as fixing of printing material is unnecessary; and so on.
More specifically, the ink-jet printing method disclosed in Japanese Patent Application Laid-Open No. 54-51837 and German Publication (DOLS: Deutschland Offenlegungsschrift) No. 2843064, has a different feature from those of other ink-jet printing methods in the way that it provides heat energy to ink liquid to generate driving force for ink discharge.
Furthermore, according to the printing method disclosed in the above-mentioned patent publications, the liquid activated by heat energy changes its state due to rapid increase in volume. Driving force generated by the change in the state causes discharging of the liquid from an orifice provided at the end of a printhead, forming a discharging droplet, and the droplet adheres to a print medium to form a pixel, thereby executing printing.
The printing method disclosed in DOLS No. 2843064 is not only effectively applied to so-called drop-on-demand printing, but also readily realizes printing performed by a full-line type printhead having multiple orifices integrated in high density, where the print width of the printhead is as large as the width of the print medium. Therefore, the printing method provides advantages in that an image having high resolution and high quality can be obtained at high speed.
The printhead adopting aforementioned printing method is configured with: an orifice provided to discharge liquid, a nozzle connected to the orifice and including a liquid channel having a heating unit as a part of its structure to generate heat energy to act on the liquid and discharge a droplet, and a substrate integrating an electrothermal transducer (heater) serving as means for generating heat energy.
Lately, such substrate of a printhead not only integrates a plurality of heaters, but also integrates drivers which drive each of the heaters, shift registers which can store image signals having the number of bits equal to the number of heaters to parallelly transfer these serially-inputted image signals to respective drivers, and a logical circuit such as a latch circuit or the like which temporarily stores data outputted by the shift registers.
FIG. 14 is a block diagram showing configuration of a logical circuit of a printhead having 32 heaters (printing elements), which is capable of printing at the conventional density, 360 dpi.
Referring to FIG. 14, reference numeral 400 denotes a substrate; 401, heaters (H1-H32); 402, power transistors; 403, a 32-bit latch circuit; and 404, a 32-bit shift register. Reference numeral 415 denotes a sensor which monitors resistance values of the heaters 401 and temperature of the substrate 400, and also denotes a heater for keeping the substrate 400 warm. A plurality of such sensors and heaters may be provided. Reference numerals 405 to 414-n respectively denote input/output pads. Reference numeral 405 denotes a clock input pad for inputting a clock signal (CLK) to drive the shift register 404; 406, an image data input pad for serially inputting image data (DATA); 407, a latch input pad for inputting a latch clock signal (LTCLK) in order to latch image data in the latch circuit 403; 408, a driving signal input pad for inputting a heat pulse (HEAT) in order to externally control driving timing by turning on the power transistor 402 and sending an electric current to the heaters 401; 409, a driving power input pad for supplying driving power (3V-8V, generally 5V) for the logical circuit; 410, a GND terminal; 411, a heater's power input pad for supplying power to the heaters 401; and 412, a reset input pad for inputting a reset signal (RST) to initialize the latch 403 and shift register 404.
In addition, reference numerals 413-1 to 413-8 denote block-selecting-signal input pads for inputting block-selecting signals (BLK1-BLK8) which select a block at the time of the time-divisional drive control where the 32 heaters 401 are divided into eight blocks to be driven. Reference numerals 414-1 to 414-n denote output pads of monitor signals and input pads of control signals for controlling driving of sensors and driving of heaters provided to maintain internal temperature of a printhead.
Next, description will be provided on a driving sequence of a printhead having the above-described configuration. Herein, image data (DATA) is assumed to be binary data where one pixel is expressed by one bit.
When the main unit of a printer, incorporating the printhead, serially outputs image data (DATA) in synchronization with a clock signal (CLK), the data is inputted by the shift register 404. The inputted image data (DATA) is temporarily stored in the latch circuit 403, which then outputs ON/OFF signal in correspondence with a value ("0" or "1") of the image data.
Herein, when a block is selected by a block-selecting signal (BLK1-BLK8), if a heat pulse (HEAT) is inputted while an output of the latch circuit 403 is "ON," the corresponding power transistor 402 is driven for the length of time the heat pulse (HEAT) is "ON." Accordingly, current is supplied to the corresponding heaters 401 to heat ink whereby discharging ink droplets.
FIG. 15 is a timing chart showing the driving timing in a case where 32 heaters (H1, H2, . . . H32) are provided, and are divided into eight blocks (each block having four heaters H1-H4, H5-H8, . . . , H29-H32) to be driven by time-divisional drive control by the block-selecting signals (BLK1-BLK8). The waveform illustrated in FIG. 15 only shows, among the signals transmitted from the printer' main unit, the block-selecting signals for time-divisional drive control and the heat pulse (HEAT) for deciding a length of time to drive the heater 401.
When the output of the latch circuit 403 is "ON," all the heaters, being divided into blocks, are driven once in one print cycle at slightly different timings by the control signals. On account of such time-divisional drive control, the number of heaters to be driven simultaneously is reduced, the capacity of the power source is reduced, and noise generated at the time of driving is reduced.
As the printer and printhead are further diversified and developed in the future to meet various needs, such as low price, capability to express a complicated image having high quality and high resolution and so on, it is necessary that various printers can use various types of printheads, instead of utilizing a dedicated printhead for each printer. To cope with the diversification of printheads, efforts have been made to standardize connecting portions among the printers and printheads. Nevertheless, the printer was merely able to distinguish the type of printhead that is being installed.
Moreover, reflecting upon the recent tendency to prefer high-quality image printing, the main subject of development and manufacturing of the printhead is now turning into print density of 600/720 dpi from the conventional density 300/360 dpi. Therefore, the latest printhead requires new configuration for a substrate which is different from that of the aforementioned conventional printhead, in terms of arraying pitch of heaters (printing elements), drivers, logical circuits or the like.
On the other hand, as long as printheads are used as consumables, a manufacturer must keep producing printheads having conventional print density which was produced and sold in the past, even if a printer incorporating the conventional printhead is no longer manufactured. Therefore, the types of printheads manufacturers must produce rapidly increase.
The above-described tendency is quite inefficient in terms of production efficiency of printheads, resulting in increase in manufacturing cost. In addition, when a user purchases a printhead to replace an old printhead, the user tends to have difficulties determining which type of printhead to purchase.